System and method of operation for network overlay geolocation system with repeaters

ABSTRACT

A novel system and method for a network overlay geolocation system operating in a host wireless communication system with repeaters ( 350   a   , 350   b ) is disclosed. Embodiments of the novel system and method enable the geolocation system to determine if signals being received by the geolocation system arrive directly from a target mobile appliance or if the signals are passing through a repeater ( 350   a   , 350   b ) and therefore are subject to a known time delay. Embodiments of the novel system and method provide a more accurate geolocation of mobiles served by repeater stations than capable in the prior art.

CROSS REFERENCES

The present application is co-pending with and claims priority benefitof provisional application entitled “Geolocation of Mobile Appliances”,Application Ser. No. 60/418,342 and filed on 16 Oct. 2002, and theprovisional application entitled “System and Method for Network OverlayGeolocation System with Repeaters in a GSM Network”, Application Ser.No. 60/503,490 and filed on 17 Sep. 2003, the entirety of each is herebyincorporated herein by reference.

The present application is related to and concurrently filed withapplications titled “A NETWORK OVERLAY GEO-LOCATION SYSTEM WITH SMARTANTENNAS AND METHOD OF OPERATION” 10/531,040, “A SYSTEM AND METHOD FORENHANCING THE ACCURACY OF A LOCATION ESTIMATE” 10/531,044 , “NETWORKOVERLAY LOCATION SYSTEM AND METHOD FOR AIR INTERFACE WITH FREQUENCYHOPPING” 10/531,041, “A SYSTEM AND METHOD FOR ESTIMATING THE MULTI-PATHDELAYS IN A SIGNAL USING A SPATIALLY BLIND ANTENNA ARRAY 10/531,039, and“WIRELESS COMMUNICATION NETWORK MEASUREMENT DATA COLLECTION USINGINFRASTRUCTURE OVERLAY-BASED HANDSET LOCATION SYSTEMS” 10/531,042, filedOct. 16, 2003, the entirety of each of these applications isincorporated herein by reference.

BACKGROUND

Applicant's disclosure is directed generally towards a wirelesscommunications network overlay for determining the location of mobileappliances.

The use of wireless communication devices such as telephones, pagers,personal digital assistants, laptop computers, etc., hereinafterreferred to collectively as “mobile appliances”, has become prevalent intoday's society. Recently, at the urging of public safety groups, therehas been increased interest in technology which can determine thegeographic position, or “geolocate” a mobile appliance in certaincircumstances. For example, the Federal Communication Commission (FCC)has issued a geolocation mandate for providers of wireless telephonecommunication services that puts in place a schedule and an accuracystandard under which the providers of wireless communications mustimplement geolocation technology for wireless telephones when used tomake a 911 emergency telephone call (FCC 94-102 E911).

In addition to E911 emergency related issues, wirelesstelecommunications providers are developing location-enabled servicesfor their subscribers including roadside assistance, turn-by-turndriving directions, concierge services, location-specific billing ratesand location-specific advertising.

To support FCC E911 rules to locate wireless 911 callers, as well as thelocation enabled services, the providers of wireless communicationservices are installing mobile appliance location capabilities intotheir networks. In operation, these network overlay location systemstake measurements on RF transmissions from mobile appliances at basestation locations surrounding the mobile appliance, and estimate thelocation of the mobile appliance with respect to the base stations.Because the geographic location of the base stations is known, thedetermination of the location of the mobile appliance with respect tothe base station permits the geographic location of the mobile applianceto be determined. The RF measurements of the transmitted signal at thebase stations can include the time of arrival, the angle of arrival, thesignal power, or the unique/repeatable radio propagation path (radiofingerprinting) derivable features. In addition, the geolocation systemscan also use collateral information, e.g., information other than thatderived for the RF measurement to assist in the geolocation of themobile appliance, i.e., location of roads, dead-reckoning, topography,map matching etc.

In a network-based geolocation system, the mobile appliance to belocated is typically identified and radio channel assignments determinedby (a) monitoring the control information transmitted on radio channelfor telephone calls being placed by the mobile appliance or on awireline interface to detect calls of interest, i.e., 911, (b) alocation request provided by a non-mobile appliance source, i.e., anenhanced services provider. Once a mobile appliance to be located hasbeen identified and radio channel assignments determined, the locationdetermining system is first tasked to determine the geolocation of themobile appliance and then directed to report the determined position tothe requesting entity or enhanced services provider.

The monitoring of the RF transmissions from the mobile appliance orwireline interfaces to identify calls of interest is known as “tipping”,and generally involves recognizing a call of interest being made from amobile appliance and collecting the call setup information. Once themobile appliance is identified and the call setup information iscollected, the location determining system can be tasked to geolocatethe mobile appliance.

FIG. 1 shows a conventional mobile-appliance communication system havingbase stations 10 a-c for communicating with a mobile appliance 20. Eachbase station 10 contains signal processing equipment and an antenna fortransmitting to and receiving signals from the mobile appliance 20 aswell as other base stations. A Base Station Controller (“BSC”) and/orMobile Switching Center (“MSC”) 45 typically is connected to each basestation 10 through wireline connection 41. A mobile appliance locationdetermining sensor 30 i.e., wireless location sensor (“WLS”) may bepositioned at some or all of the base stations 10 to determine thelocation of mobile appliance 20 within the signal coverage area of thecommunication system. A network overlay system is generally composed oftwo main components, one that resides at the base station that makesmeasurements on the RF signal emanating from the wireless device, theWLS 30, and one that resides at the mobile switch that tasks the WLSgroups to collect data and then uses the data to compute a locationestimate, this latter component is generally referred to as theGeolocation Control System (“GCS”) 50. In the normal course ofoperation, the GCS is tasked by an outside entity, e.g., the MobilePositioning Center (“MPC”) 40, to generate a location estimate on aparticular mobile appliance. The tasking is accompanied by informationon the mobile of interest including the serving base station and sectorfor the call and the RF channel (frequency, time slot, CDMA code, etc.)being used by the wireless communications network to complete thewireless connection. Once the GCS receives this tasking, based on theserving sector, it tasks a set of WLS units to make measurement on theRF emission of the mobile. The WLS units make the measurements, andreport them to the GCS. The GCS then computes a location estimate usingsome mathematical or data matching algorithm. Alternatively, controlsignaling on RF or wireline interfaces used to set up calls in thewireless network can be scanned to detect the placement of a call ofinterest. The signaling that occurs on the RF control channel can beused to determine location, or call setup/channel assignment parameterscan be extracted from the control messaging to determine which trafficchannel to use for location related measurements.

Network overlay location systems typically locate a mobile appliance onthe traffic channels of a wireless network. The system typically usessensors employing techniques of time difference of Arrival (“TDOA”)supplemented with Angle of Arrival (“AOA”) in some case to perform amulti-site location computation. The traffic channel assignmentinformation is provided through a separate process, with one optionbeing a wireline interface providing MOBINFO (IS-41 Mobile Information)parameters passed by the Mobile Positioning Center as part of theGPOSREQ (J-STD-036 Geolocation Position Request) message from the MPC tothe GCS 50.

To meet the ever growing demand for mobile communication, wirelesscommunication systems deploy repeater stations to expand range andconcentration of coverage. In FIG. 1, a repeater 50 a, associated withbase station 10 a, is located to extend the coverage area to encompassthe back side of the mountain 1. The repeater 50 b, associated with basestation 10 c, is mounted on a building and is used to provide servicewithin the building 2.

Repeaters typically fall into two categories: (1) non-translating, alsoknown as wideband, and (2) translating, also known as narrowband. Asshown in FIG. 2 a, non-translating repeater 250 simply passes theforward F_(f1) and reverse R_(f1) frequencies from the base station 210and mobile appliance 220 respectively to and from the repeater coveragelocation. Often wideband repeaters are “in-building” or serve limitedcoverage areas. While the description of non-translating repeaters aboveand translating repeaters below are described in reference to frequency,their operation can equally be described in terms of channels, and theuse of the term frequency should not be construed to limit the scope ofthe present disclosed subject matter.

A translating repeater assigns the mobile to a different traffic channelunbeknownst to the base station, mobile switch, MPC, and the basestation controller. As shown in FIG. 2 b, the translating repeater usesthe base station traffic channel R_(f1) for repeater 250 to base station210 communication while the mobile appliance 220 utilizes a separatefrequency R_(f2) for mobile to repeater communications. Translatingrepeaters act similarly in the forward direction using F_(f1) from thebase station 210 to the repeater station 250 and F_(f1) from therepeater station 250 to the mobile appliance 220. In both cases, theexistence of the repeater is usually transparent to the network.

Repeaters typically communicate with the host base station via an RFlink as shown in FIG. 3 between base station 310 and repeater 350 a.This connection allows remote operation of the repeater without physicalties back to the host base station, which is particularly advantageousin rugged or other areas where laying lines are difficult or costly.Some repeaters, generally non-translating repeaters, use a fiber opticor copper wire “tether” instead of an RF link to communicate with thehost base station as shown in FIG. 3, where base station 310 isconnected to repeater station 350 b by tether 351. RF signals are placedonto the tether at the repeater, and then summed into the normal basestation antenna path at the antenna feed interface 311 at the host basestation. After integration into the normal base station antenna path,the signal from the repeater is indistinguishable to the base stationregarding its origin (e.g., from the base station antennas or from atether). In this tether architecture as well, the host base station hasno knowledge of the repeater's existence or that a call is being servedby the repeater.

Neither the base station nor the switch knows that a repeater is servinga call. Therefore the GPOSREQ information from the MPC which, in part,originates from the switch, is not able to alert the Geolocation systemthat a repeater is in use. When a prior art network overlay locationsystem attempts to locate a mobile being served by a repeater withoutknowing that a repeater is serving the mobile, a number of alternativescan occur. The location system may locate the mobile based on receivingonly RF signals directly from the mobile at a sufficient number of sitesto locate the mobile. This alternative is the same as if the repeaterwas not involved from the standpoint of the location system. Anotheralternative is that the location system would receive signals from therepeater backhaul link antenna, and produce a location. Thus, thelocation of the repeater antenna (rather than the mobile) would be the“worst case” geolocation computed location. For example, a repeaterinstalled as an in-building distribution system would use indoorantennas to communicate with the indoor handsets, and an outdoor antennato communicate with the host base station. If the geolocation systemwere unable to locate the mobile itself, the location of the outdoorantenna (the repeater) would be used. Since this is the location of thebuilding housing the mobile, this is a much better location estimatethan the Phase I cell-sector information and is often compliant withinthe FCC accuracy mandate over the given network. The Phase I systemtypically does not know of repeater existence and uses the host cell'scell-sector information for location. While acceptable in some cases, asidentified above, using the location of repeater 50 a in FIG. 1, wouldbe of little use. In the case where the location system receives the RFsignal from a mixed set of sources (some from the mobile and some fromthe repeater backhaul antenna), an erroneous location estimate can begenerated. In the case where the location system does not receive RF atsufficient WLS sites to generate a location estimate due to the effectsof the repeater action or transmitted power of the mobile ordirectionality of the repeated signal from the repeater backhaulantenna, no location estimates will be reported.

Therefore, there is a need in the prior art for a network overlaygeolocation system and method of operation in a host wirelesscommunication system that provides accurate geolocation of mobilesserved by repeater stations. In order to accomplish this, there is aneed to overcome the deficiencies in the prior art by employing a novelgeolocation system and method that is capable of identifying when amobile's signal is being received via a repeater.

In view of this need, it is an object of the disclosed subject matter toobviate the deficiencies in the prior art and present an improved methodfor determining the location of a mobile appliance in a wirelesscommunication system with base stations and a repeater for communicatingwith the mobile appliance. The wireless communication system includes amobile positioning center and the repeater is connected with acommunication tether to the base station. A plurality of geolocationsensors are co-located with the plural base stations and the mobilepositioning center provides mobile information to the geolocationsystem. The improvement includes the step of monitoring thecommunication system with the WLS and determining if a target mobileappliance is served by the at least one repeater.

It is also an object of the disclosed subject matter to present animproved method of determining the location of a mobile appliance in awireless communication system having base stations and repeater stationsfor communicating with the mobile appliance. The repeater station isconnected to the base stations with a communication tether. Theimprovement includes the steps of detecting signals from a target mobileappliance on the communication tether and using a known delay attributedto the communication tether and the respective repeater station todetermine the location of the target mobile appliance.

It is another object of the disclosed subject matter to present animproved method for determining the location of a mobile appliance in awireless communication system with base stations and repeater stationsfor communicating with the mobile appliance where a repeater station isconnected to its base stations with a communication tether. Theimprovement includes determining the location of the repeater stationusing mobile information parameters received from an MPC and using thelocation of the repeater station, or the centroid of the repeater'scoverage area, as the location of the mobile appliance.

It is still another object of the disclosed subject matter to present animproved method for determining the location of a mobile appliance in awireless communication system with base stations and repeaters. Themethod includes the step wherein the repeater station relays a mobileappliance's signal on a different channel than the signal transmitted bythe mobile appliance. The improvement includes relaying from therepeater station information regarding the channel of the mobileappliance's signal to a geolocation system and using the information todetect the mobile appliance's signal or repeater backhaul antenna signaland calculate the mobile appliance's location.

It is yet another object of the disclosed subject matter to present animproved method for determining the location of a mobile appliance in awireless communication system with base station and repeaters, where therepeaters relay the mobile appliance's signal on the same channel as thechannel in which the signal was received by the repeater, and where amobile positioning center provides mobile information to assist in thelocation of the mobile appliance. The improvement includes using thefirst signal received from the mobile appliance at each of the pluralbase stations to determine the location of the mobile appliance.

It is an additional object of the disclosed subject matter to present anovel network overlay geolocation system for locating a mobile in a hostwireless communication system. The host wireless communication systemincludes a base station and a repeater station connected by acommunication tether. The network overlay geolocation system has ageolocation sensor attached to the communication tether between the basestation and said repeater station.

It is also an additional object of the disclosed subject matter topresent a novel wireless communication system for providingcommunication to and from a mobile appliance. The system includes a basestation and a repeater station interconnected by a communication tetherconnected to the base station at an antenna feed interface and a mobilepositioning center for providing mobile information. The network overlaygeolocation system has a geolocation sensor co-located at the basestation on the tether prior to the antenna feed interface.

These objects and other advantages of the disclosed subject matter willbe readily apparent to one skilled in the art to which the disclosurepertains from a perusal or the claims, the appended drawings, and thefollowing detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art wireless communication system with a networkoverlay geolocation system.

FIG. 2 a is an illustration of the operation of a non-translatingrepeater station.

FIG. 2 b is an illustration of the operation of a translating repeaterstation.

FIG. 3 is an illustration of a wireless communication system withrepeater stations connected with an RF link and over a tether.

FIG. 4 is an illustration of a geolocation sensor integrated into a basestation before the antenna feed interface.

DETAILED DESCRIPTION

An important aspect of the presently disclosed subject matter is thatthe geolocation system can determine when a received signal from amobile has passed through a repeater. Prior art systems do not have thiscapability and consequently treat all the signals received by thegeolocation system as having been received directly from the targetmobile. For example, the ability to determine if a signal from a mobilehas passed through a repeater enables embodiments of the disclosedsubject matter to determine in some instances (a) at least a defaultlocation of a mobile (e.g., at the repeater) where the prior art coulddetermine no location at all, and/or (b) a location of the mobile wherethe prior art may return a location with large errors. The foregoing areexemplary only and shall not be used to limit the invention. Theseexamples and others are discussed in more detail below.

Since the presently-disclosed subject matter is capable of determiningwhether a signal received from a mobile has passed through a repeater,geolocation systems using the present subject matter can betterdetermine the location of a mobile appliance.

In a wireless communication system utilizing a repeater, a geolocationsystem of one embodiment of the present subject matter can compute thelocation of the mobile appliance itself and only fall back to therepeater's location (which may be, for example, the location of therepeater's electronics, the location of the repeater's antenna, or thelocation of the centroid of the repeater's coverage area) a lowpercentage of the time. This is accomplished by having the geolocationsystem focus on and use the signal(s) arriving earlier in time at thegeolocation sensor locations for TDOA, AOA or other type of locationmethod discussed herein when later-arriving signal(s) are delayed by anamount approximately equal to the repeater delay. As is known in theart, repeaters add some time delay to the mobile signal, whether therepeater is translating or non-translating, tethered or untethered(sometimes referred to herein as RF Backhaul). The delay arises from thefact that the repeater receives a signal from the mobile, reproduces (ortranslates) and amplifies the signal, and then transmits the signal tothe base station. Therefore, in most cases, signals that travel directlybetween the mobile and a geolocation system arrive earlier in time, byapproximately a known amount (i.e., the repeater delay), before signalsthat travel from the mobile to the geolocation system through arepeater.

Likewise, in a wireless communication system utilizing a repeater, ageolocation system of another embodiment of the present subject mattercan compute the location of the mobile appliance itself and only fallback to the repeater's location a low percentage of the time. In thisembodiment, the repeater puts a tag on the mobile signal that passesthrough the repeater. The tag can be any type of tag added to a signalas is well known in the art. One non-limiting example consistent withthis discussion is the timing advance (“TA”) measurement in a GSM mobilecommunication system. The geolocation system receives the repeatedsignal, recognizes the repeater's tag and consequently knows that thesignal is a repeated signal with a repeater delay associated therewith,and processes the signal accordingly (i.e., the geolocation system“operates” on the tag). In this embodiment, it is not necessary todetermine the difference in times of arrival of direct signals andrepeated signals at the geolocation system.

The ability to discern the difference between direct signals andrepeated signals (i.e., signals that arrive via a repeater) in either ofthe above-mentioned embodiments allows for the geolocation system tobetter determine a location for the mobile. In some instances, therepeater signals may be ignored. As a non-limiting example, if mixedsignals (i.e., both direct signals and repeated signals) are received atthe geolocation system, the geolocation system may default to the directsignal(s) and locate the mobile without reference to the repeatedsignal.

It will be useful to compare prior art systems with systems operating inaccordance with the present subject matter. As will be shown below, theinability of the prior art to determine if a mobile's signal has beenreceived via a repeater may result in severe errors in the geolocationestimate. The following Table 1 indicates what a typical prior artsystem will output since the prior art is incapable of determining thepresence of a repeater in a wireless communication system. It will beunderstood by those of skill in the art that Table 1 below (and thefollowing Tables 2 and 3) assume that the only location information isderived from the target mobile's signal:

TABLE 1 Non-Translating Repeater Scenario RF Backhaul Tethered (1) GCSReceives Measurements from Target Mobile Only: (a) <3 signals receivedNo geolocation No geolocation determined determined (b) ≧3 signalsreceived Determine Determine geolocation of geolocation of mobile mobile(2) GCS Receives Measurements from Repeater Only: (a) <3 signalsreceived No geolocation No geolocation determined determined (b) ≧3signals received Determine Determine geolocation of geolocation ofrepeater repeater (3) GCS Receives Measurements from Both Mobile andRepeater: (a) <3 signals received No geolocation No geolocationdetermined determined (b) ≧3 signals received Possible large Possiblelarge errors in errors in geolocation geolocation

Regarding Table 1 above, it will be noted that only non-translatingrepeaters are shown in Table 1. Table 1 does not include translatingrepeaters since the prior art has no way of dealing with translatingrepeaters since the prior art does not, for example, include a mechanismto track the translation of the frequency due to the translatingrepeater. Therefore, without knowledge of the proper frequency for themobile, a reported geolocation may actually be based in part on energynot attributable to the target mobile. Consequently, the determinedgeolocation may be highly inaccurate and the prior art would have no wayof knowing that a problem exists.

It will be obvious to those of skill in the art that since the prior artcannot determine if there is a repeater being used in the system, thenthe prior art cannot determine the difference between signals receiveddirectly from the mobile and signals received via a repeater. Therefore,the prior art cannot distinguish between, for instance, Scenario (1)(b),in which the geolocation of the mobile is actually determined andScenario (2)(b), in which the geolocation of the repeater is actuallydetermined. In both Scenarios, the prior art system will report that thegeolocation of the mobile has been determined. Similarly, Scenario(3)(b) is likewise indistinguishable from either Scenario (1)(b) orScenario (2)(b). However, Scenario (3)(b) will most likely have largeerrors due to the unaccounted for time delay in the measurement(s) thatarrived at the GCS via a repeater. Additionally, the prior art can makeno determination of geolocation in the event less than 3 measurementsare received by the GCS, consistent with the assumption stated above.

The following table, Table 2, indicates what one embodiment of thedisclosed subject matter will output when a repeater is operating in awireless communication system. In this embodiment, there is a knowndifference in time of arrival between a signal from the target mobileappliance that is received by the geolocation system directly from themobile and a signal from the mobile that is received by the geolocationsystem via a repeater.

TABLE 2 Translating Repeater Do Not Non-Translating Repeater Know KnowScenario RF Backhaul Tethered Translations Translations (1) GCS ReceivesMeasurements from Target Mobile Only: (a) <3 signals received Nogeolocation Determine No geolocation N/A determined repeater determinedlocation in some instances (b) ≧3 signals received Determine DetermineDetermine N/A geolocation of geolocation of geolocation of mobile mobilemobile (2) GCS Receives Measurements from Repeater Only: (a) <3 signalsreceived No geolocation Determine Determine N/A determined repeaterrepeater location in location in some instances some instances (b) ≧3signals received Determine Determine Determine N/A geolocation ofgeolocation of geolocation of repeater repeater repeater (3) GCSReceives Measurements from Both Mobile and Repeater: (a) <3 signalsreceived Determine Determine Determine N/A repeater repeater repeaterlocation in location in location in some instances some instances someinstances (b) ≧3 signals received Determine Determine DetermineDetermine mobile mobile location mobile location repeater location inlocation in some instances some instances

A comparison of Table 1 (prior art) and Table 2 (an embodiment of thepresent subject matter, designated generally as Embodiment Alpha)indicates that the present subject matter can determine a usefullocation for the mobile appliance more often (and more accurately) thanthe prior art. For example, the prior art for Scenario (3)(a), fornon-translating repeaters, cannot determine any location for the mobile.However, Embodiment Alpha can, in some instances, output as the mobile'slocation the location of the repeater. When, through measuring TOA fromboth the direct path and the repeater, it can be determined that themobile is in the proximity of the repeater. As discussed elsewhereherein, the location of the repeater typically is within acceptablegeolocation parameters. As another example, the prior art for Scenario(3)(b), for non-translating repeaters, may output a geolocation for themobile that has large errors, as discussed above. However, EmbodimentAlpha may determine the mobile's location in some instances where TOAsfrom both the direct path and through the repeater are measured and theTOAs from the direct path are used to determine the position of themobile. Furthermore, the prior art cannot determine a location for themobile in any Scenario when a translating repeater is in use. EmbodimentAlpha can determine the location of the mobile as indicated in Table 2so long as the geolocation system has knowledge of the translationsbeing used. If the translations are not known, then Embodiment Alphacannot determine the location of the mobile, as indicated by “N/A” (“NotApplicable”) in Table 2.

The following table, Table 3, indicates what another embodiment of thedisclosed subject matter will output when a repeater is operating in awireless communication system. In this embodiment, a repeater places atag on the signal passing through it that the geolocation system canrecognize and therefore know that the associated signal is a repeatedsignal.

TABLE 3 Translating Repeater Do Not Non-Translating Repeater Know KnowScenario RF Backhaul Tethered Translations Translations (1) GCS ReceivesMeasurements from Target Mobile Only: (a) <3 signals received Nogeolocation Determine No geolocation N/A determined repeater determinedlocation (b) ≧3 signals received Determine Determine Determine N/Ageolocation of geolocation of geolocation of mobile mobile mobile (2)GCS Receives Measurements from Repeater Only: (a) <3 signals receivedDetermine Determine Determine N/A repeater repeater repeater locationlocation location (b) ≧3 signals received Determine Determine DetermineN/A geolocation of geolocation of geolocation of repeater repeaterrepeater (3) GCS Receives Measurements from Both Mobile and Repeater:(a) <3 signals received Determine Determine Determine N/A repeaterrepeater repeater location location location (b) ≧3 signals receivedDetermine Determine Determine Determine mobile mobile location mobilelocation repeater location in location in some instances some instances

A comparison of Table 1 (prior art) and Table 3 (an embodiment of thepresent subject matter, designated generally as Embodiment Beta)indicates that the present subject matter can determine a usefullocation for the mobile appliance more often (and more accurately) thanthe prior art. For example, the prior art for Scenario (3)(b), fornon-translating repeaters, may output a geolocation for the mobile thathas large errors, as discussed above. However, Embodiment Beta maydetermine the mobile's location in some instances where TOAs from boththe direct path and through the repeater are measured and the TOAs fromthe direct path are used to determine the position of the mobile. Asdiscussed elsewhere herein, the location of the repeater typically iswithin acceptable geolocation parameters. Furthermore, the prior artcannot determine a location for the mobile in any Scenario when atranslating repeater is in use. Embodiment Beta can determine thelocation of the mobile as indicated in Table 3 so long as thegeolocation system has knowledge of the translations being used. If thetranslations are not known, then Embodiment Beta cannot determine thelocation of the mobile, as indicated by “N/A” (“Not Applicable”) inTable 3.

In the case of an RF backhaul repeater, neighboring repeaters are notused by the geolocation system to participate in location measurements,since no sensor hardware is typically installed at the repeater sites,rather adjacent cell cites participate. The delay imposed by therepeaters serving a call not only would cancel out during timedifference of arrival calculations, but the signal would likely beignored since the repeater signals are received after the mobile'ssignal, therefore the delay does not need to be known. Alternatively,the delay value can be known, and kept in a database and compensated forduring time difference calculations, if it is known that the signalreceived was from the repeater, for instance where topology effectivelyprevents the mobile's signal from being received at the base stationsuch as is depicted in FIG. 1 with regards to repeater 50 a.

Tethered repeater installations do not utilize a RF link forcommunication back to the base station, but rather use a fiber optic orcopper tether as a back haul. In this scenario, a geolocation systemsensor is connected at the host base station to the repeater RF signalprior to the antenna feed interface connection at the base station. FIG.4 shows the location of the geolocation sensor for a repeater tetheredto a base station. The base station 410 which includes the antennas 412receives the antenna output at an antenna feed interface 411. In theembodiment shown, the geo location sensor 430 is located upstream of theantenna feed interface 411. The signal from the mobile appliance 420 isreceived at repeater station 450 with antenna 452. The signal isrepeated over the communication tether 451 to the base station 410. Thegeolocation sensor is located prior to or at the antenna feed interface411 or more particularly before the antenna feeds are summed togetherand supplied to the base station 410. For the purposes of thisapplication, the antenna feed interface is defined as the point at whichthe antenna outputs are summed and the origin is no longerdistinguishable. While the embodiment shown in FIG. 4 shows one sensor,a plurality of sensors can be used at the base station or a sensor thatswitches across the inputs to the base station is equally envisioned.The location of the geolocation sensor allows the geolocation system todetermine when a call is served by a repeater, as well as utilizeneighboring repeaters to assist with the location of the mobile sincethese neighboring repeaters will be receiving the actual mobile signal,not the signal transmitted from the serving repeater and their actualdelay times are known.

As with the RF link repeater type, neither the base station nor theswitch is aware that a repeater is serving the call. Therefore theGPOSREQ information from the MPC is not able to alert the geolocationsystem that a repeater is in use. The geolocation system locates thetransmitter using the corresponding MOBINFO parameters passed from theMPC. The sensor at the base station is able to determine when a repeateris serving a call, since the mobile's signal is intercepted on thetether prior to being added to the antenna feeds of the base stationsantennas. This information allows the geolocation system the ability toadapt the sensors participating in a location to account for thetethered repeater by adjusting the TOA, among other things, andcalculate the location of the mobile transmitter.

In the tethered link repeater instance, the signal delay of the repeateras well as any fiber or copper tether lines must be known and stored inthe geolocation system database. These delays are advantageouslydetermined experimentally, however empirical or theoretical delay valuescan also be incorporated. The geolocation system takes these delays intoaccount when computing the TDOA location of the mobile. Since delayinformation is known, neighboring repeaters may be used as TDOA sensorsites to aid in the mobile location. This is the only scenario where thedelay of the repeater components needs to be known. This differs fromthe case of an RF link, where neighboring repeaters are not used as TDOAsensor sites and thus their delay information is not required. Asdiscussed previously the delay imposed by these repeaters serving acall, cancels out during time difference calculations.

In the translating repeater case, neither the base station nor theswitch know that a repeater is serving a call, nor do they know thefrequency on which the phone is transmitting. Therefore the GPOSREQinformation from the MPC is not able to alert the geolocation systemthat a repeater is in use or the frequency of the target mobile. Rather,the geolocation system locates the transmitter using the correspondingMOBINFO parameters passed from the MPC, which in the case of a mobileserved by a translating repeater, is the location of the repeaterantenna (rather than the mobile). The “worst case” geolocation systemcomputed location would also be the “best case” geolocation systemcomputed location. As the case with the wideband repeater this worstcase estimate is sometimes a much better location estimate than thePhase I cell-sector information and is often compliant within the FCCaccuracy mandate over the given network. The Phase I system typicallydoes not know of repeater existence and used the host cell's cell-sectorinformation for location. Greater accuracy can be achieved fortranslating repeaters by establishing communication with the repeaterequipment to gather mobile transmitter frequency information. If thegeolocation system is aware of the mobile's frequency, or otheridentifying signal characteristic, the system can search for themobile's signal at other base stations or repeaters, and if a tetheredrepeater, can use known system time delays to determine the TDOA or AOAcalculations. Otherwise, the location of the translating repeater isgiven as the location. Alternatively, if economical, a translatingrepeater's translation can be mapped and stored in a database accessibleto the geolocation system, however, such mapping may be difficult in asystem that dynamically allocates channels.

While preferred embodiments of the present inventive system and methodhave been described, it is to be understood that the embodimentsdescribed are illustrative only and that the scope of the embodiments ofthe present inventive system and method is to be defined solely by theappended claims when accorded a full range of equivalence, manyvariations and modifications naturally occurring to those of skill inthe art from a perusal hereof.

1. A method of determining the location of a mobile appliance in awireless communication system having plural base stations and at leastone repeater for communicating with the mobile appliance, and a mobilepositioning center, wherein a plurality of geolocation sensors areco-located with the plural base stations, and wherein the at least onerepeater is connected with a communication tether to the base station,and the mobile position center provides mobile information to thegeolocation system, the improvement comprising the step of monitoringthe communication system with the geolocation system and determining ifa target mobile appliance is served by the at least one repeater,wherein the geolocation sensors monitor the tether between the at leastone repeater and an antenna feed interface for the mobile appliance'ssignal.
 2. The method of claim 1 wherein the mobile appliance's signalis a traffic signal.
 3. The method of claim 1 wherein the mobileappliance's signal is a reverse pilot signal.
 4. The method of claim 1wherein the mobile information is control information.
 5. The method ofclaim 4 wherein the control information is call set up information ormobile registration process information.
 6. A method of determining thelocation of a mobile appliance in a wireless communication system havingplural base stations and at least one repeater for communicating withthe mobile appliance, and a mobile positioning center, wherein aplurality of geolocation sensors are co-located with the plural basestations, and wherein the at least one repeater is connected with acommunication tether to the base station, and the mobile position centerprovides mobile information to the geolocation system, the improvementcomprising the step of monitoring the communication system with thegeolocation system and determining if a target mobile appliance isserved by the at least one repeater; and, adjusting the time of arrivalof the mobile appliances signal based on the determination if the mobileappliance is being served by the one of the at least one repeaters. 7.The method of claim 6, further comprising the step of adjusting the timeof arrival of the mobile signal at the geolocation sensor with knowntime delays of the at least one repeater and communication tether. 8.The method of claim 7, further comprising the step of adjusting the timeof arrival of the mobile signal at another of the plural geolocationsensors with known time delays of another one of the at least onerepeater and respective communication tether.
 9. The method of claim 6,further comprising the step of accessing with the geolocation sensorsthe known time delays from a database.
 10. The method of claim 7,wherein the adjusted time of arrivals are used by the geolocationsensors in determining the location of the mobile appliance.
 11. Amethod for determining the location of a mobile appliance in a wirelesscommunication system having plural base stations and plural repeaters,wherein the repeaters relay the mobile appliances signal on the samechannel as the channel in which the signal was received, and where amobile positioning center provides mobile information to assist in thelocation of the mobile appliance, the improvement of using the firstsignal received from the mobile appliance at each of the plural basestations to determine the location of the mobile appliance anddisregarding a second signal received from the mobile appliance at eachof the plural base stations when determining the location of the mobileappliance.
 12. The method of claim 11, wherein the channel is defined bya frequency.
 13. The method of claim 11, wherein the channel is definedby a time slot.
 14. The method of claim 11, wherein the channel isdefined by a spreading code.
 15. A network overlay geolocation systemfor locating a mobile in a host wireless communication system, said hostwireless communication system having a base station and a repeaterstation connected by a communication tether, said network overlaygeolocation system comprising a geolocation sensor attached to thecommunication tether between said base station and said repeaterstation.
 16. A wireless communication system providing communication toand from a mobile appliance comprising: a base station and a repeaterstation interconnected by a communication tether; a mobile positioningcenter for providing mobile information; a network overlay geolocationsystem with a geolocation sensor co-located at the base station; whereinsaid tether is connected to said base station at an antenna feedinterface, and said geolocation sensor is located on said tether priorto said interface.
 17. A method of determining the location of a mobileappliance in a wireless communication system having plural base stationsand at least one repeater for communicating with the mobile appliance,where the wireless communication system has a network overlaygeolocation system operably connected thereto, comprising the steps of:determining whether a signal received from the mobile appliance by thegeolocation system has passed through a first repeater, wherein pluralsignals are received from the mobile appliance by the geolocation systemand said first repeater is a tethered repeater; determining if one ofthe plural signals has passed through the first repeater is based inpart on a difference between the times of arrival of two of the pluralsignals at the geolocation system, said time difference beingapproximately equal to a known repeater time delay; attaching a tag tothe mobile appliance's signal that passes through the first repeater;determining if one of the plural signals has passed through the firstrepeater is based in part on the geolocation system operating on thetag; and determining the location of the mobile appliance based in parton the determination of whether a signal received from the mobileappliance by the geolocation system has passed through the firstrepeater.